The present invention relates to a composition for removing side wall and method of removing side wall, more specifically, the present invention relates to a composition for removing side wall, which can remove a side wall deposit (side wall) containing resist polymer and inorganic substances, generated at dry etching using halogen-type gas in the production process of a semiconductor, at a low temperature within a short time while not corroding the wiring material, a method of removing side wall using the composition and a method of producing semiconductor devices comprising the step of removing side wall using the composition.
A semiconductor device is conventionally produced using a photoresist resin as shown in FIG. 2 (a) to (f), for example, through the following steps (1) to (6):
(1) a metal layer which works out to a wiring material, such as Al, is formed on an insulating layer such as SiO2 on a substrate 1 (FIG. 2 (a));
(2) a positive photoresist 4 is formed on the metal layer 3 (FIG. 2 (b));
(3) a photomask 5 is superposed thereon and the photoresist layer is exposed (FIG. 2 (c));
(4) the photoresist layer is developed to form a resist pattern (FIG. 2 (d));
(5) the exposed metal layer is etched (FIG. 2(e)); and
(6) the resist pattern is stripped and removed to obtain a metal wiring pattern (FIG. 2 (f))
To keep up with the tendency in recent years toward higher density of the integrated circuit, formation of a finer pattern is necessary. In the etching step, wet etching by using chemicals has heretofore predetermined, but wet etching is not appropriate for forming a finer pattern because etching direction is not oriented. For forming a finer pattern, dry etching, especially dry etching by using a halogen-type gas such as chlorine gas or BCl3 which is capable of anisotropic etching is taking the place of it.
In the dry etching, film comprising resist polymer and inorganic substances is formed on the side of metal and resist pattern on the metal as shown in FIG. 3 (a). The remained film is called side wall, and the side surface is protected by this side wall therefore, anisotropic etching can be used. The side wall is produced by the chemical reaction of photoresist, wiring material and etching gas at the dry etching. As a result, the side wall assumes a compound having a complicated composition comprising an organic material derived from the photoresist, an inorganic material derived from the wiring material and a halide derived from etching gas.
In the dry etching, in order to completely remove the remained photoresist, an ashing operation (ashing) where the remained photoresist is burned with oxygen plasma after dry etching step, is conducted, but the side wall is not completely removed and a part of it remained (FIG. 3(b)). In the side wall, halogen radical or halogen ion generated at the dry etching with a halogen-type gas is imprisoned and on contacting with water in air, generates an acid. The acid generated corrodes the wiring material (after-corrosion). Because of this, the side wall must be completely removed.
The stripping solution is originally designed to strip the photoresist which is an organic material, therefore, it cannot satisfactorily strip and remove the above-described side wall.
For example, an acidic stripping solution of alkylbenzene-sulufonic acid type cannot satisfactorily remove the side wall even under heating at a high temperature of 100xc2x0 C. Moreover, the acidic stripping solution has low solubility in water and must be rinsed with a water-soluble organic solvent such as IPA before water rinsing, as a result, the process is complicated.
An alkaline stripping solution of organic amine type also has difficulties in removing the side wall even under heating at a high temperature of 100xc2x0 C. Furthermore, if the resulting substrate is immediately rinsed with water, the organic amine component and water interact to present strong alkalinity and corrosion of the wiring material is generated. Accordingly, the substrate must be rinsed with IPA or the like in advance of water rinsing, as a result, the process is complicated.
U.S. Pat. No. 5,308,745 (JP-A-6-202345) proposes a stripping composition for highly crosslinked or cured photoresist comprising a stripping solvent such as 2-pyrrolidinone, an amine and a weak acid, and JP-A-7-219240 proposes a positive resist-stripping solution obtained by blending a carboxyl group-containing organic compound with a resist-stripping compositon comprising a nitrogen-containing organic hydroxyl compound. However, as described above, the resist-stripping solution cannot satisfactorily remove the side wall. Furthermore, although an acid such as hydrochloric acid and sulfuric acid, or a base such as aqueous alkylamine and alkanolamine solution may remove the side wall by dissolving the aluminum as a wiring material, they indispensably corrode the wiring material.
Under these circumstances, a stripping solution capable of easily removing a side wall produced by anisotropic dry etching after the formation of photoresist without corroding the wiring material is demanded. The side wall is produced as a result of chemical reaction of photoresist, wiring material and etching gas and assumes a compound having a complicated composition comprising an organic material derived from photoresist, an inorganic material derived from wiring material and a halide derived from etching gas.
The object of the present invention is to provide a composition for removing side wall capable of removing a side wall at low temperature within a short time while not corroding the wiring material, method of removing side wall using the composition and method of producing semiconductors.
As a result of extensive investigations, the present inventors have found that side wall can be removed at low temperature within a short time while not corroding the wiring material by use of a liquid composition comprising nitric acid which by itself corrodes the wiring material, and a polycarboxylic acid, an aminocarboxylic acid or a salt thereof. The present invention has been accomplished based on this finding.
Thus, the present invention relates to a composition for removing side wall, method of removing side wall and method of producing semiconductors as described below.
(1) A composition for removing side wall which comprises an aqueous solution containing nitric acid and at least one kind of carboxylic acids selected from polycarboxylic acid, aminocarboxylic acid and salts thereof.
(2) The composition for removing side wall as described in 1 above, wherein the concentration of said nitric acid is from 0.01 to 50 wt %.
(3) The composition for removing side wall as described in 2 above, wherein the concentration of said nitric acid is from 0.1 to 50 wt %.
(4) The composition for removing side wall as described in 1 above, wherein the concentration of said carboxylic acids is from 0.0001 to 30 wt %.
(5) The composition for removing side wall as described in 4 above, wherein the concentration of said carboxylic acids is from 0.1 to 30 wt %.
(6) The composition for removing side wall as described in 1 above, wherein said polycarboxylic acid or polycarboxylate is an aliphatic polycarboxylic acid or an aliphatic polycarboxylate.
(7) The composition for removing side wall as described in 1 above, wherein said polycarboxylic acid or polycarboxylate is an aromatic polycarboxylic acid or an aromatic polycarboxylate.
(8) The composition for removing side wall as described in 1 above, wherein said aminocarboxylic acid or aminocarboxylate is an aliphatic aminocarboxylic acid or an aliphatic aminocarboxylate.
(9) The composition for removing side wall as described in 1 above, wherein said polycarboxylic acid or polycarboxylate is at least one selected from the group consisting of citric acid, tartaric acid, malic acid, succinic acid, maleic acid, oxalic acid, malonic acid, glutanic acid, adipic acid, D-glucanic acid, itaconic acid, citraconic acid, mesaconic acid, 2-oxoglutaric acid, 3-oxoglutaric acid, acetylenedicarboxylic acid, 1,1-cyclopropanedicarboxylic acid, trimellitic acid, endothal, glutamic acid, methylsuccinic acid, citramalic acid and salts thereof.
(10) The composition for removing side wall as described in 1 above, wherein said aminocarboxylic acid or aminocarboxylate is at least one selected from glycine, alanine, xcex2-alanine, 2-amino-butyric acid, 3-amino-butyric acid, 4-amino-butyric acid, 2-aminocapronic acid, 6-aminocapronic acid, and salts thereof.
(11) The composition for removing side wall as described in any one of 1, 7 or 9 above wherein said polycarboxylic acid is citric acid.
(12) The composition for removing side wall as described in any one of 1, 8 or 10 above wherein said aminocarboxylic acid is glycine.
(13) The composition for removing side wall as described in 1 above, wherein the carboxylic acids are polycarboxylic acid and aminocarboxylic acid.
(14) The composition for removing side wall as described in 13 above, wherein said polycarboxylic acid is citric acid and said aminocarboxylic acid is glycine.
(15) A method of removing side wall comprising cleaning treatment of the side wall generated at the dry etching step in a production process of semiconductors with the composition for removing side wall as described in any one of 1 to 14 above.
(16) The method of removing side wall as described in 15 above, wherein the cleaning treatment is made by dipping.
(17) The method of removing side wall as described in 16 above, wherein the cleaning treatment is operated within a temperature of 0 to 80xc2x0 C.
(18) The method of removing side wall as described in 17 above, wherein the cleaning treatment is operated within a temperature of 10 to 60xc2x0 C.
(19) The method of removing side wall as described in 16 above, wherein the cleaning treatment is operated within a period of 1 to 60 minutes.
(20) The method of removing side wall as described in 19 above, wherein the cleaning treatment is operated within a period of 1 to 30 minutes.
(21) A process for producing a semiconductor device comprising a step of the cleaning treatment of the side wall generated at the dry etching step in the production process of the semiconductors using the composition for removing side wall as described in any one of 1 to 14 above.
(22) The process for producing a semiconductor device as described in 21 above, wherein the semiconductor device has Al alloy wiring.
(23) The process for producing a semiconductor device as described in 21 or 22 above, wherein the semiconductor device has Al alloy wiring which is not substantially corroded.
(24) A semiconductor device having substantially uncorroded Al alloy wiring which is obtained by the cleaning treatment of the side wall generated at the dry etching step in the production process of the semiconductor device using the composition for removing side wall as described in any one of 1 to 14 above.